A STUDY  OF  THE  GARBON  DEPOSITS 
FOUND  IN  THE  CYLINDERS  OF 
INTERNAL  COMBUSTION 
ENGINES 


GLENN  HOWE  JOSEPH 


THESIS 


FOR  THE 


DEGREE  OF  BACHELOR  OF  SCIENCE 

IN 

' CHEMICAL  ENGINEERING 


COLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 


UNIVERSITY  OF  ILLINOIS 


1922 


' 


/ 92  2, 
J 77 


UNIVERSITY  OF  ILLINOIS 


— .May 2& 1922. 


THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 

G on  _ H q w e _ J o s eph 

ENTITLED A _ STUDY  0 F _THE_  CARBON  _DEPOS  I_TS_  THAT  _ARE_  POUND 

IN  _ _t_HE  _ CYLINDERS  _ OJF_  1 HTPRNAL  _ COMBUST  ION_  ENG IKES  # 

IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 

DEGREE  OF  BACHELOR. _OP_S_CIENCE 

IN  CHEMICAL  ENGINEERING 


ACTING  HEAD  OF  DEPARTMENT  OF  _CHMXSTRY 


Tiie  writer  desires  sincerely  to  express  his 
appreciation  of  the  aid  and  encouragement  given  in 
connection  with  this  thesis  hy  Dr.  T.E.  Layng. 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/studyofcarbondepOOjose 


TABLE  OF  CONTENTS 


page 

1.  INTRODUCTION 1 

2.  HISTORICAL 4 

3.  THEORETICAL 7 

4.  EXPERIMENTAL... 

(a)  The  Sample.,.....,..,.....,.  11 

(h)  Loss  at  105°  C 11 

(c)  Proximate  Analysis. ........ . 13 

(d)  Ultimate  Analysis 17 

(e)  Acidity 18 

(f)  Variation  of  Results........  18 

5.  DISCUSSION  OF  RESULTS 19 

6 . SUMMARY 24 

7.  BIBLIOGRAPHY 25 


A STUDY  OF  THE  CARBON  DEPOSITS  FOUND  IN 
THEJ  CYLINDERS  OF  INTERNAL  COMBUSTION  ENGINES 

I . INTRODUCTION 

The  gasoline  engine  has  been  more  than  a score  of 

years  in  reaching  its  present  state  of  development.  From 

being  a novelty,  it  has  grown  to  be  a necessity.  Automobiles 

have  increased  from  1,000,000  in  1912,  to  9,000,000  in  1920 

--over  one  million  yearly  increase.  For  this  nine  fold  increase 

in  automobiles,  there  has  been  only  a two  fold  increase  in 

the  production  of  crude  oil.'^  The  investigators  of  the 

United  States  Geological  Survey,  after  very  exhaustive  tests, 

2 

say  that  in  1934,  the  6,000,000,000  barrels  of  crude  oil  now 
underlying  the  United  States,  willbe  exhausted,  based  on  the 

1920  rate  of  production.  This  increase  since  1909  may  be  ex- 

. 1 
pressed  as : 

Crude  oil  140$ 

Gasoline  800$ 

Automobiles  2570$ 

All  owners  of  gasoline  engines,  whether  in  a vehicle 
or  of  the  stationary  type,  have  experienced  trouble  with  the 
formation  of  a deposit  in  the  engine,  commonly  called  a "Car- 
bon deposit."  This  deposit  is  evidently  a hinderance  to  the 
smooth  and  economical  running  of  the  engine,  and  hence  must 
be  taken  into  consideration  when  efforts  are  being  taken  to 
prolong  our  present  supply  of  fuel. 

"The  enormous  number  of  internal  combustion  engines  in 
use,  particularly  in  automobiles,  trucks,  and  motor  boats, 


, 

. 

: ■ • 

2. 


has  been  the  means  of  giving  a new  and  special  significance 
to  the  word  "darbon”  and  of  making  it  a household  word.  ”Car- 
’ ton"  has  come  to  mean  to  most  people,  the  deposit  which  forms 
in  the  cylinders  of  these  engines. 

There  is  perhaps  no  greater  trouble  maker  for  our 
engines  than  this  so-called  carbon  deposit.  It  is  understood 
by  the  automobile  owner  that  he  must  have  it  removed  from  his 
motor  every  six  months  or  so,  if  he  wants  to  prevent  his 
motor  from  getting  extravagant.  Power  will  decrease  and  the 
fuel  consumption  will  increase.  There  will  be  mis-firing 
due  to  the  sooty  spark  plugs.  Premature  firing  of  the 
charge  sometimes  results  from  the  incandescent  scales  and  the 
motorist’s  ’’knock”  occurs. 

With  all  these  common  troubles  due  to  it,  the  guilty 
little  deposit  goes  on  through  the  years,  with  no  one  inter- 
fering. Many  efforts  have  been  spent  in  trying  to  prevent  it-- 
sfforts  based  mainly  on  misinformation.  For  instance,  some 
people  advocate  screens  for  the  intake  manifold  to  prevent 
road  dust  from  being  drawn  into  the  cylinders,  believing  it 
to  be  the  prime  factor  in  the  formation  of  the  deposits  and 
to  constitute  a greater  portion  of  them.'* 

It  is  certain  that  no  efforts  from  an  intelligent  stand- 
point can  ever  be  made  to  eliminate  or  remove  these  deposits, 
without  first  knowing  their  composition.  Knowing  the  nature 
of  the  compounds  that  make  up  the  deposit,  it  is  possible  to 
suppose  a satisfactory  remover  for  it  could  be  prepared.  Of 
course  the  ideal  way  to  remove  the  deposits  would  be  to  cause 
complete  combustion  of  all  carbon  in  the  fuel  and  to  prevent 


3 


the  oil  from  being  carbonized. 

In  reality  these  deposits  are  not  pure  carbon  but  are 
only  about  three- fourths  pure  carbon.  The  remainder  is  made 
up  of  hydrocarbons  and  metallic  oxides,  from  the  engine. 

Some  silica  gets  in  through  the  intake  from  the  road  dust  and 
can  be  found  in  the  deposits.  The  composition  varies  from 
car  to  car,  for  different  parts  of  the  cylinder  of  the  same 
car,, and  from  season  to  season.  Sometimes  deposits  will  be 
found  that  are  asphaltic  in  appearance  and  others  will  be 
hard  and  brittle. 

The  carbon  in  these  deposits  is  evidence  that  there 
is  waste  in  the  combustion  chamber.  Carbon  is  fuel' — it  could 
be  burned  to  give  power,  and  yet  it  is  found  to  be  about 
three-fourths  of  the  deposit.  It  is  the  most  important  item 
in  the  composition  of  the  deposits,  acting  as  an  indicator  of 
incomplete  combustion  of  the  fuel. 

The  iron  content  is  an  important  factor,  showing  the 
amount  of  solution  or  wear  of  the  metal  parts  of  the  engine. 
The  cylinder  walls  and  the  piston  rings  are  attacked  and 
leakage  of  cylinder  oil  is  the  result.  In  cold  weather,  and 
in  starting  when  the  motor  isoold,  the  raw  gasoline  that  is 

allowed  to  enter  the  cylinder  and  that  is  not  decomposed, 

♦ 

flows  down  the  cylinder  wall 3 and  dilutes  the  crankcase 
oil.  Hard  crusty  deposits  are  formed  around  the  valves  and 
prevent  the  proper  seating,  causing  losses  in  compression. 


V ) . » 


. 

. 

. 


' 


4* 


II.  HISTORICAL 

There  have  been  carbon  deposits  and  carbon  troubles, 
no  doubt,  as  long  as  there  have  been  engines  using  gasoline. 
Twenty-five  years  ago  when  there  were  only  four  automobiles 
in  the  United  StateB  there  was  not  much  use  publishing  articles 
concerning  these  troubles.  It  has  been  only  since  the  motor 
vehicle  has  become  more  common  and  is  being  used  so  widely, 
that  we  hear  of  the  carbon  trouble. 

4 

In  1918  the  Blatt-Washburn  Company  had  some  work  done 
on  carbon  deposits.  They  stated  that  the  carbon  deposits  were 
not  pure  carbon,  but  contained  only  percents  varying  from  5 
to  75.  The  remainder  was  said  to  consist  of  variable  per- 
centages of  metallic  oxides  and  inactive  earthy  material. 

There  was  some  solid  compound  that  they  said  was  an  asphaltic 
material  depending  on  the  type  of  oil  used.  They  did  not  make 
a very  thorough  study  of  the  carbon  and  did  not  give  any 
specific  data. 

Another  authority^  states  "that  a chemical  analysis 

of  the  cylinder  incrustations  from  the  combustion  space  of  an 

automobile  engine,  especially  if  the  deposit  has  been  formed 

during  the  summer  months  when  the  roads  are  dusty,  will  very 

likely  show  a considerable  percentage  of  silicates  which  have 

been  introduced  in  the  form  of  road  dust.” 

§ 

Mr.  Kettering,  . T.  A.  Boyd,  and  Mr.  Midgley  of 
the  General  Motors  Research  Corporation,  have  contributed 
some  to  the  knowledge  of  this  deposit.  They  divide  the  deposit 
into  four  distinct  divisions:  free  carbon,  a hydrocarbon,  a 
material  containing  oxygen,  and  a varying  amount  of  ash. 


• • 

. 

' 


. . 


„ 

> • * 

* 

. 

, 

. 

* 

# • 

5. 

This  material  containing  oxygen  is  believed  by  them  to  be 
the  binding  compound.  They  show  how  alkaline  liquids  disin- 
tegrate the  deposits,  and  how  this  must  be  due  to  the  acid 
character  of  the  compound.  They  have  never  given  any  data 
as  to  the  further  division  of  the  deposit  for  publication, 
if  they  have  made  any  more  determinations  on  it* 

Dr.  C.  E.  Waters  and  Mr.  W.  S.  James  of  the  United 
States  Bureau  of  Standards,  have  probably  done  more  work  on 
this  subject  than  anyone  else.  They  have  issued  a bulletin 
on  “The  Carbonization  of  Lubricating  Oils"  in  which  they  dis- 
cuss some  of  the  carbon  problems.  Practically  all  the  work 
that  they  have  done  is  based  on  the  theory  that  the  deposits 
are  results  of  the  lubricating  oil.  They  have  endeavored  to 
devise  tests  that  will  give  indications  in  the  laboratory  of 
how  the  oil  will  act  in  actual  use  toward  the  deposition  of 
carbon.  As  a result  of  such  endeavors,  the  Waters  carbonization 
test  has  been  devised,  and  also  the  Conradson  "carbon  residue" 
test.  There  is  no  place  where  they  have  stated  any  definite 
data  as  to  the  composition  of  the  carbon  residue. 

In  Europe,  the  only  published  account  of  analytical 

7 

work  on  the  deposits  was  made  by  Mr.  J.  Marcusson.  He 
divides  the  deposits  into  four  divisions:  an  oily  portion  sol- 
uble in  benzene,  a brittle  asphaltic  constitutent  insoluble  in 
benzene,  a coaly  portion,  and  a mineral  ash.  By  using  a 
very  large  amount  of  solvent  he  obtained  a portion  of  the 
asphaltic  material,  and  from  it  extracted  "asphal to genic 
acids  or  anhydrides  and  found  the  residue  to  consist  of  car- 


. 

. 

* 


6 


benes  and  carboids.M 

Prom  these  three  published  accounts,  it  is  not  pos- 
sible to  gather  much  specific  data  concerning  the  chemistry 
of  the  deposits.  They  are  all  general  in  their  statements 
and  more  or  less  theoretical — none  giving  any  analytical  data. 


. 

. 


* 


7. 


III.  THEORETICAL 

It  can  be  seen  from  the  discussion  of  the  formation 
of  carbon  deposits  that  appeared  in  the  work  of  Dr.  Waters  and 
Mr.  James,  that  there  are  two  theories  for  the  cause  of  car- 
bon deposition,  both  based  on  the  supposition  that  it  is 
caused  from  the  lubricating  oil.  The  oxidation  of  the  oil  to 
form  asphaltic  matter,  which  hardens  after  collecting  metal- 
lic oxides  and  dust,  is  one  way  the  deposits  are  explained. 

The  other  theory  is  based  on  the  fact  that  after  oils  are 

subjected  to  destructive  distillation,  or  are  cracked,  there 

14 

is  a deposit  of  actual  carbon.  One  author  states  that 
carbon  deposits  are  similar  to  coal,  and  suggests  Professor 
Parr’s  method  of  extraction  by  solvents  to  bear  out  his 
statements. 

It  is  very  hard  to  collect  data  to  support  either 
theory,  due  to  the  difficulty  of  duplicating  the  exact  condi- 
tions that  exist  within  the  cylinders  during  the  combustion. 
There  are  so  many  different  makes  of  engines,  each  with  dif- 
ferent conditions  as  to  fuel  used,  oil  used,  piston  rings, 
pressure  during  explosion,  carburetor  setting  and  speed. 

These  conditions  can  only  be  standardized  on  a block  test, 
and  then  it  will  be  impossible  to  get  actual  conditions  such 
as  road  dust  and  temperature. 

Q 

One  well  known  authority  states,  "The  deposit  is  by 
no  means  due  to  the  lubricating  oil  alone,  but  comes  partly 
from  residual  products  in  the  fuels  and  its  formation  is 
probably  controlled  in  part  by  the  interaction  between  the  oil 


. 

. 

. 

4 

; ' • * 

. 

, 

' 

. 


. •)  i 

• 

„ • ’ '■ 

• . . 

i.  i.  -j  ::  .:V 


8 


and  the  fuel  residues.”  Those  supporting  the  oxidation 
theory  of  carbon  formation  show  the  effects  of  sunlight  on 

3 

the  oil,  impurities  in  the  oil  and  catalyzers  of  oxidation. 

Oils  in  the  sunlight  will  oxidize  causing  a precipitate  to 
settle.  This  precipitate  is  an  acid  substance  containing 
carbon,  oxygen  and  hydrogen.  There  are  some  "resinous” 
substances  about  which  there  is  little  known,  that  are  pre- 
sent in  the  crude  oils  or  are  formed  in  the  refining  process, 
that  are  the  most  important  of  the  catalyzers  of  oxidation  of 
oils.  By  heating,  they  polymerize  and  form  asphaltic  mat- 
ter. Iron  oxide  and  sulphur  are  very  good  catalyzers  of 
oxidation  also.  Dust  and  dirt,  when  present  in  the  oil,  cut 
down  the  percent  of  asphalt  formed  by  heating. 

Cracking  of  oils,  or  the  breaking  down  of  the  heavy 

molecules,  is  favored  by  high  temperatures  and  pressures.  In 

the  cylinders  we  have  high  temperatures  and  pressures.  The 

thin  films  of  oil  exposed  to  the  influences  of  the  cylinder 

during  the  explosion  easily  "crack”  and  the  volatile  products 

that  are  formed  dilute  the  oil  or  are  burned.  The  heavy 

residues  are  left  behind  to  build  up  the  deposits.  Asphaltenes 

9 

are  found  in  carbon  deposits.  Holde  showed  that  the  amount 
of  carbonization  depended  on  the  proportion  of  asphaltenes 
present  in  the  oils. 

Compared  to  the  very  small  amounts  of  lubricating  oil 
that  enter  the  combustion  chambers,  there  are  large  amounts 
of  gasoline  vapor-air  mixtures.  A study  of  the  conditions  that 
are  present  in  this  vapor-air  mixture  in  the  operation  of  the 


. 

' 

* 

* 

, 


. 

■ 

. 

, 

■ 


9 


engine  would  probably  lead  to  the  conclusion  that  the  deposits 
are  due,  more  from  the  gasoline  than  from  the  oil. 

The  fundamental  idea  of  all  combustion  practice  is  to 
furnish  just  enough  air  for  the  complete  combustion  of  all 
the  carbon.  Where  there  is  not  enough  air,  there  will  be  in- 
complete combustion  and  a resulting  smoke  of  unburned  carbon 
particles.  The  nearer  the  boiling  point  the  fuel  can  be  rais- 
ed, the  more  vaporization  that  will  take  place.  In  the  engine 
the  vaporization  is  increased  by  allowing  the  pressure  to  fall 
by  the  suction  stroke  of  the  piston.  The  charge  of  vapor  and 
air  is  then  put  under  pressure  and  ignited  by  the  aid  of  an 
electric  spark.  The  added  pressure  causes  the  temperature 
to  raise  and  at  the  same  time  lower  the  temperature  at  which 
the  charge  will  ignite.  When  the  engine  is  first  started, 
the  temperature  is  not  high  enough  to  cause  all  the  charge  to 
ignite.  The  driver,  on  noticing  that  his  engine  is  failing, 
entiches  the  mixture  of  gasoline  and  air  by  allowing  less  air 
to  enter.  The  temperature  will  increase  due  to  the  smaller 
amount  of  air  entering.  As  the  temperature  increases  the 
viscosity  of  the  gasoline  decreases  and  the  volume  of  the  air 
increases.  This  causes  a double  concentration  of  gasoline 
vapor.  As  a result  of  this  enrichment,  there  will  not  be 
enough  air  for  complete  combustion  and  the  attendant  smoke 
formation  and  carbon  deposition  will  take  place.  As  the 
temperature  increases  there  will  also  be  an  increase  in  the 
decomposition  of  the  hydrocarbons  in  the  fuel.  At  a temperature 
of  1500°C,  0.036  seconds  is  the  time  required  for  the  complete 


‘ . 


. 

. 

. 

. 

. 

. 


, ' 

. 

. 


10 


decomposition  of  the  hydrocarbons  and  a deposition  of  carbon.1^ 
Mr.  C.  E.  Sargent,1^  a research  engineer  of  Indiana- 
polis, has  shown  how  the  decomposition  of  hydrocarbons  takes 
place  even  when  the  best  carburetting  devices  known  were  used. 
He  took  down  an  engine  and  cleaned  the  combustion  chamber  per- 
fectly, reassembled  it  and  drove  the  car  slowly  for  five  miles. 
The  engine  was  again  taken  down  and  it  was  found  that  there 
was  a smooth  deposit  of  soot  or  carbon  all  over  the  inner 
surface  of  the  chamber.  Thermometers  had  been  inserted  in 
the  most  critical  places  during  the  test  and  it  was  found 
that  there  were  no  places  where  the  temperature  of  the  metal 
of  the  cylinder  walls  was  over  150°C.  At  this  tdmperature 
it  is  impossible  to  get  any  burning  of  the  lubricating  oil 
and  a carbon  deposit.  Mr.  Sargent  also  used  as  a fuel,  fixed 
gases,  as  illuminating  gas,  and  found  after  long  runs,  there 
was  no  carbon  forming  in  the  cylinders. 

In  view  of  the  contradictory  opinions  that  are  held 
concerning  the  formation  of  carbon  in  the  cylinders  of  internal 
combustion  engines,  this  thesis  was  undertaken  in  an  attempt 
to  show  that  the  deposits  were  the  result  of  incomplete  com- 
bustion of  the  fuel  and  not  results  of  lubricating  oil  pro- 
ducts. 


■ 

V. 


11. 


IV.  EXPERIMENTAL 

(a) The  Sample 

The  samples  were  collected  from  various  garages  in 
this  city  and  in  other  cities.  Garage  men  were  supplied  with 
bottles  fitted  with  good  stoppers.  They  saved  the  carbon 
they  took  from  cars  and  were  careful  to  keep  it  as  free  from 
foreign  matter  as  they  could.  After  several  weeks  the  bottles 
were  collected  and  the  whole  mass  of  material  was  carefully 
ground  together  and  mixed  well.  This  sample  was  then  labelled 
"Number  1",  and  no  more  additions  were  made  to  it  later  on. 
Other  samples  were  collected  from  time  to  time  and  were  kept 
in  the  laboratory  in  tightly  stoppered  bottles.  The  results 
given  in  this  thesis  are  from  one  of  these  samples.  The 
variation  ih  composition  of  the  different  samples  is  shown  in 
Table  9. 

b)  Loss  at  105°C.  for  one  hour 

The  sample  was  put  in  small  moisture  capsules,  those 

used  for  moisture  determinations  in  coal,  and  heated  in  an 

oven  at  a temperature  of  105°C.  for  one  hour.  The  loss  was 

3.68$  of  the  weight  of  the  sample.  In  order  to  ascertain 

the  material  that  was  given  off  at  these  conditions,  the 

following  method  was  used:  Fifteen  (15)  grams  of  the  sample 

were  put  in  a small  Erlenmeyer  flask  fitted  with  two  outlet 

tubes.  In  the  flask  was  forced  a slow  stream  of  nitrogen, 

purified  by  passing  through  pyrogallol  and  then  through  CaClg. 

On  the  other  side,  the  gases  coming  out  of  the  flask,  passed 

through  a weighed  U-tube  filled  with  CaC^,  through  an  ordinary 

cylindrical  CaCl  tube,  and  into  a receiving  bottle.  The 

6 


* 


. 


. 


. 


. 


. 


. 

# 


< 

, 

. . J 


second  drying  tube  prevented  any  moisture  from  the  receiving 
aspirators  from  backing  up  into  the  weighed  U-tube  if  the  stream 
of  nitrogen  stopped.  In  heating  the  flask  to  105°C,  a beaker 
of  glycerine-water  solution  boiling  at  this  temperature  was 
used.  In  making  the  determination,  a liter  or  so  of  nitrogen 
was  passed  through  the  apparatus  first  in  order  to  completely 
displace  all  the  air,  that  is  before  the  collecting  bottle 
was  attached. 

lOOcc  of  this  gas,  mainly  nitrogen  added,  were  analyz- 
ed in  a modified  Orsat  apparatus,  where  the  percentages  of 
carbon  dioxide,  oxygen,  ethylene,  benzene,  hydrogen,  carbon 
monoxide,  methane  and  ethane  were  determined.  These  percen- 
tages were  then  calculated  to  a nitrogen  free  basis  so  as  to 
eliminate  the  low  percentages  due  to  the  nitrogen  added  and 
to  show  the  true  composition  of  the  gases  that  passed  through 
the  CaClg  tube.  The  moisture  collected  was  weighed  and  its 
percentage  calculated.  The  results  are  shown  in  Table  1 and 
Table  2: 

TABLE  1. 

Analysis  of  material  driven  off  at  105° C.  1 hour 

% original  sample  * % of  the  loss 

» 

i 


Moisture  1.51  41.0 

Gases  by  wt.  2.17  59.0 

lOO.O 


(Table  2 - see  next  page) 


13 


TABLE  2. 

Analysis  of  the  gases  from  Table  1. 

Gas  % by  volume  of  the  gas 


Oxygen 

5.8 

Benzene 

5.8 

CO  2 

34.6 

Paraffins 

53.8 

100  .0  (value  of  n - 1.03 

(c)  Proximate  Analysis 

A proximate  analysis  was  made  showing  the  material  to  fall 
into  three  main  groups,  shown  in  Table  3.  The  ash  is  the  term 
that  is  applied  to  the  material  that  remained  in  a crucible 
after  all  the  combustible  matter  had  been  driven  off  by  ignit- 
ing over  a blast  lamp  until  no  change  in  weight  occurred.  The 
dishes  which  were  used  were  very  shallow  and  wide.  If  deep 
dishes  were  used,  like  ordinary  porcelain  crucibles,  it  was 
found  very  difficult  to  completely  oxidize  all  the  carbon. 

By  playing  a small  stream  of  oxygen  over  the  crucible  during 
the  heating,  it  was  possible  to  get  checking  figures  comparing 
to  the  ash  obtained  in  shallow  dishes.  The  samples  were  usual- 
ly of  one  gram,  although  by  carefully  etirring  with  nichrome 
wires,  and  using  oxygen,  it  was  possible  to  get  good  results 
with  samples  as  large  as  fifteen  grams. 

TABLE  3. 

Proximate  Analysis  of  Original  Sample. 


Given  off  at  105°C.  (1  hr.)  3.68# 

Ash 9.76 

Combustible  matter 86.56 


TOW 

A further  division  of  the  sample  was  made  by  means 


14 


ef  a Soxhlet  Extraction  apparatus.  Samples  from  different 
automobiles,  different  localities,  and  from  different  seasons 
of  the  year,  were  found  to  contain  varying  amounts  of  oil.  Some 
were  hard  and  brittle,  while  others  were  very  oily,  or  MwetM. 
These  were  treated  in  the  ordinary  Soxhlet  with  different 
solvents,  benzene,  toluene,  carbon-tetrachloride,  and  pyridine. 
The  percentage  of  extraction  varied  over  a range  from  19$  to 
29$  with  the  average  at  21.00$. 

TABLE  4. 

Division  of  Sample  by  Extraction, 


Extractable  with  Benzene  21.00$ 

Residue  from  extraction 79.00 


166.66 

The  residue  from  the  thimble  was  d(i|r|ed  in  an  electric 
oven  at  a temperature  sufficient  to  drive  off  all  the  sol- 
vent, for  one  hour.  It  was  then  treated  to  determine  the  com- 
position. Carbon  was  determined  by  the  combustion  method  of 
Liebig,  using  lead  chromate  and  copper  oxide  in  the  combus- 
tion tube,  as  sulphur  was  thought  to  be  present.  Hydrogen 
was  also  found  by  this  method,  absorption  in  35$  KOH.  Sulphur 
was  determined  by  the  use  of  the  Parr  Peroxide  Bomb;  at  the 
same  time  checks  were  run  on  the  carbon  by  treating  the 
fusion  in  a Parr  Total  Carbon  apparatus  and  later  the  sulphur 
precipitated  from  an  acid  solution  by  BaClg  and  weighed  as 
BaSO^  . The  ash  was  obtained  in  the  manner  stated  for  the 
original  sample.  The  results  for  the  analysis  of  the  residue 
from  the  Soxhlet  extraction  are  shown  in  Table  5. 


• ' 


■ 


15 


TABLE  5. 

Analysis  of  the  material  remaining  after  washing 
with  benzene. 


# original  sample  » % of  the  residue 


Carbon  60.13  76.11 

Hydrogen 3.31  4.19 

Sulphur 1.32  1.68 

Oxygen 6.95  8.80 

Ash 7.29  9.22 

W.o6  106.06 


The  extract  was  distilled  in  a distilling  flask  to 
drive  off  the  solvent  and  enable  the  extracted  matter  to  be 
analyzed.  The  residue  from  the  extraction  was  black  and  had 
the  appearance  of  asphalt.  It  was  placed  in  a boat  and  an 
analysis  on  the  combustion  furnace  was  run.  This  gave  the 
percentages  of  carbon  and  hydrogen  directly.  The  boat  was 
weighed  after  the  determination  to  get  the  percentage  of  the 
little  red  powder  that  remained.  The  powder  was  found  to  be 
iron  oxide  by  qualitative  tests.  It  had  evidently  been  in 
the  colloidal  condition  in  the  extract.  Sulphur  that  pro- 
bably was  present,  was  oxidized  to  SOg  and  absorbed  by  the 
lead  chromate.  The  results  are  given  in  Table  6. 

TABLE  6. 

Analysis  of  the  material  extracted  with  benzene. 


% original  sample  • % of  the  extract 


Carbon  11,46  54.57 

Hydrogen  1.94  9.25 

Sulphur  .06  .28 

Iron  .05  .27 

Oxygen  7.49  35.63 

21.00  100. 00 


16 


The  percentages  of  carbon,  hydrogen  and  oxygen  as 
shown,  give  proportions  for  a compound  of  this  type,  (C5Hg02)n 

The  percentage  of  sulphur  as  shown,  was  calculated 
in  the  following  manner:  The  sulphur  originally  present  in 

the  sample  had  to  go  into  the  residue  or  into  the  extract. 

There  was  a percentage  of  1.68  sulphur  found  in  the  residue, 
which  figured  back  tothe  basis  of  the  original  sample  by 
multiplying  the  percent  resid^u j 79.00,  by  the  sulphur  percent, 
1.68,  obtaining  the  amount  that  was  not  in  the  residue,  which 
equals  0.06  percent  of  the  total  sulphur  on  the  original 
basis.  The  original  sulphur  will  be  shown  later  to 

be  1.38$.  This  difference  of  0.06  percent  was  figured  back 
on  the  basis  of  the  extract  being  100#  by  dividing  it  by 
the  percent  extract,  21.00,  this  produced  the  amount  shown 
above,  0.28  percent  that  must  be  in  the  matter  extracted  by 
the  benzene. 

The  ash  obtained  by  the  ashing  dish  method,  was  anal- 
yzed. It  had  the  appearance  of  iron  oxide,  red  powder,  very 
fine  and  heavy*  This  material  was  put  into  solution  by  us- 
ing strong  hydrochloric  acid.  The  iron  was  determined  by 
the  permanganate  method  and  by  the  gravimetric  method  of 
weighing  as  the  oxide  after  precipitating  as  the  hydroxide. 

For  the  permanganate  method,  the  ash  was  treated  with  hydro- 
chloric acid  and  stannous  chloride  to  hasten  and  to  get  a 
better  solution  of  the  oxide.  In  all  cases,  it  was  necessary 
to  boil  the  acid.  Silica  was  obtained  by  filtering  off  the 
residue  that  remained  after  all  the  iron  had  dissolved  and 
washing  carefully.  The  precipitate  was  ignited  in  a small 


17. 

crucible  to  constant  weight  and  then  hydrofluoric  and  sul- 
furic acids  were  added  and  the  crucible  carefully  heated 
again.  The  loss  in  weight  was  found  to  be  the  percent  silica. 
All  the  residue  in  the  crucible  disappeared  by  this  treat- 
ment showing  that  there  was  no  other  elements  present.  The 
analysis  of  the  ash  gave  values  as  shown  in  Table  7. 

TABLE  7. 

Analysis  of  the  Ash 


% original  sample 

» . 

\ % of  the  aBh 

Iron  Oxide  8.19 

84.01 

Silica 1.54 

15.88 

5773 

A qualitative  analysis  of  the  sample  was  made  at  the 


first.  It  showed  that  there  were  no  metals  present  except 
iron.  In  one  sample  there  was  a test  for  nickel,  probably 
that  came  from  the  nickel-steel  valves  in  the  engine.  Silica, 
sulphur,  iron,  carbon,  sulphuric  acid  and  carbonic  acid  were 
found, 

(d)  Ultimate  Analysis. 

Starting  with  the  original  sample  the  percentages 
of  the  elements  were  determined,  irrespective  of  the  com- 
pounds in  which  they  occurred.  The  sample  was  dried  at  105°C. 
and  the  dried  material  run  in  a Parr  Eomb  for  the  estimation 
of  the  carbon  by  the  Parr  T0tal  carbon  apparatus  and  sulphur 
by  gravimetric  means.  Samples  were  treated  by  the  combus- 
tion method  to  get  the  carbon  and  hydrogen,  also.  The  silica 
was  determined  in  the  ash  and  the  percentages  calculated 


. 

, 

, 


. 

» 

. 

18. 

back  to  the  original  basis  by  dividing  by  the  percent  ash.  This 
gives  for  the  ultimate  analysis,  the  values  as  shown  in  Table  8. 

TABLE  8. 

Ultimate  analysis  of  the  original  sample: 


Total  carbon  . . TSTfif? 

Hydrogen  4.57 

Iron  5.74 

Sulphur  1.38 

Silica  1.55 

Oxygen  (diff.)  14.56 

I00.061 


(e)  Acidity  of  Sample 


Several  grams  of  the  sample,  not  dried,  were  placed  in  a 
flask  and  digested  with  200cc  of  distilled  water  at  a tempera- 
ture under  the  boiling  point  of  water,  in  order  not  to  drive  off 
any  carbonic  acid.  After  several  hours,  the  solution  was  fil- 
tered and  the  precipitate  washed  until  free  from  any  acid  that 
could  be  present.  The  solution  was  titrated  by  phenolphthalein  in 
the  cold.  There  was  a distinctly  acid  property  apparent.  If 
the  material  was  boiled  several  hours  in  a reflux,  the  acidity 
was  lowered.  Methyl  orange  did  not  give  as  good  values  as 
Phenolphthalein.  The  acidity  was  expressed  as  the  number  of 
milligrams  of  KOH  necessary  to  neutralize  one  gram  of  the 
sample.  The  KOH  used  was  0.0787  normal.  The  acid  numbers  var- 
ied on  different  samples  from  7.9  to  16.4 

TABLE  9. 

Showing  the  range  of  variation  in  composition  for  dif- 
ferent samples. 


Total  carbon  68.50$ 

Hydrogen  4.2 

Iron  3.8 

Sulphur 45 

Silica 50 


TT/OCT 

5.5 

6.8 

3.50 

2.00 


V.  DISCUSSION  OF  RESULTS 


19. 


Samples  from  small  cars  where  poorly  refined  oils 

and  fuels  had  been  used,  could  not  be  distinguished  from 

samples  taken  from  the  cylinders  of  engines  where  only  the 

best  of  oil  and  gasoline  had  been  used.  It  has  been  supposed 

that  oils  with  low  viscosity  would  give  deposits  more  readily 

than  oils  with  high  viscosities,  but  no  difference  could  be 

found  in  the  deposits  formed  by  the  two  oils.  This  adds  to 

12 

the  proof  of  F.  C.  Robinson's  statement  j "The  amount  of 

carbon  averages,  broadly,  about  the  same  for  low  viscosity 

and  high  viscosity  oils  and  about  the  same  for  Texas  field 

oil  and  Pennsylvania  oil;  and  the  consistency  of  the  four 

samples  of  carbon  is  identical.”  This  statement  was  later 

confirmed  by  the  United  States  Bureau  of  Standards,  where  it 

was  found  that,  "The  layers  of  carbon  which  formed  on  the 

piston  were  so  much  alike  in  their  properties  and  appearance 

3 

that  they  gave  no  hint  as  to  the  nature  of  the  oil  used.” 

Both  these  statements  were  made  from  data  based  more  on  the 
physical  property  and  general  appearance  than  on  the  chemical 
constitution.  Data  obtained  by  using  methods  described  in 
this  thesis,  proves  from  a chemical  standpoint  that  there  is 
no  relation  between  the  carbon  deposits  and  the  type  of  oil 
used  in  lubrication. 

The  outstanding  feature  of  the  results  of  this  thesis 
is  the  fact  that  all  lubricating  oils  give  identical  carbon 
deposits,  chemically.  Of  course,  there  are  samples  where  the 
oil  is  held  in  combination  more  closely  than  in  others  caused 
by  having  too  much  gasoline  and  oil  in  the  cylinders.  After 


. 


. 


. 


, 


. 


. 

. 


. 


. 


20, 

this  extra  oil  had  been  washed  out,  the  residue  was  of  nearly 
a fixed  composition.  If  the  oil  is  responsible  for  the 
deposits,  how  can  this  be  explained?  It  was  shown  how  the 
temperatures  of  the  combustion  chamber  were  so  low  that  no 
oil  could  be  carbonized,  i.e.  oil  in  contact  with  the  cylinder 
walls,  where  the  temperature  was  never  over  150°C.  It  was 
shown  how  carbon  results  from  improper  combustion  of  the 
fuel,  and  that  incomplete  combustion  took  place  in  the 
engine.  Experiments  were  described  where  fixed  gases  were 
used  as  fuel  and  where  no  carbon  deposition  resulted. 

These  facts  stand  out  as  clear  evidence  that  the  cause  of  the 
carbon  deposits  lies  in  the  incomplete  combustion  of  the 
gasoline  and  not  in  the  lubricating  oil.  Mechanical  engineers 
will  have  to  give  better  means  of  obtaining  good  combustion 
or  the  chemist  will  have  to  regulate  the  reactions  taking 
place  in  the  cylinders  and  so  control  the  decomposition  pro- 
cess. 

Iron  was  found  to  be  present  in  amounts  running  up  to 
six  percent.  This  is  rather  hi^ier  than  could  be  expected 
from  the  actual  wearing  of  the  metal  parts  of  the  engine. 

The  conditions  are  such  in  the  combustion  chamber  that  there 
could  be  formed  the  carbide  of  iron.  Around  the  exhaust 

9 

valves  the  temperature  is  over  the  minimum  required  for 
the  formation  of  the  compound  Fe^C,  and  it  is  here  that  the 
carbide  probably  first  forms.  It  is  extremely  hard  and  when 
it  gets  on  the  valves,  it  acts  as  an  abrasive  and  causes 
excess  wear  of  the  valves. 


, 


* 

. 


. . 


. 


. 

. 


. 


. 


. 


. 


- 


21. 

The  silica  content  of  the  samples  varied  very  much. 

Some  samples  with  only  0.50$  were  found  while  some  went  as 

high  as  2.00$.  The  content  of  silica  varied  very  little  for 

samples  taken  from  cars  that  had  been  in  the  city  all  the 

time.  It  is  the  constitutent  that  was  expected  to  be  found 

high,  after  reading  some  of  the  discussions  of  the  carbon 

4 

question  in  the  popular  magazines.  One  author  asserts, 

"There  are  much  higher  percentages  of  road  dust  than  oil 

residues."  This  compound  has  been  placed  in  the  deposits  by 

supposition  by  many  of  the  authors.  For  instance,  one 
5 

author  states,  "As  long  as  the  tractor  engineer  realizes 
that  dust  is  one  of  the  most  destructive  elements  to  engines, 

IT  FOLLOWS  that  such  road  dust  (silicates)  WILL  be  found  in 
the  carbon  deposits." 

The  percentages  of  sulphur  are  very  significant. 

In  one  case  the  sulphur  ran  up  to  3.50$.  This  is  surprising 
from  the  fact  that  there  is  such  a low  percentage  of  sulphur 
in  the  oil  and  gasoline.  The  men  at  the  Bureau  of  Standards 

1 2 

report  having  found  as  high  as  4.00$  sulphur  in  some  deposits. 

It  has  been  shown^4  that  where  oils  have  a low  carbonization 
value  by  the  Waters  test,  the  sulphur  content  is  low,  falling 
under  0.10$.  These  facts  show  that  the  sulphur  has  a strong 
tendency  to  pile  up  in  the  deposits,  rather  than  to  pass  out 
in  the  exhaust  as  might  be  expected.  The  relation  of  sulphur 
and  the  formation  of  asphalt  in  nature,  may  bear  some  relation 
to  this  high  sulphur  content. 

The  acid  values  of  the  deposits  are  very  important. 

There  are  two  causes  apparent.  The  sulphur  in  the  form  of  a 


• 

• 

. 

. 

. 

, 

• 

. 

• 

, 

♦ 

. 

c 

t 

. 

.. 

. 


22. 

soluble  sulfate  is  able  to  cause  a greater  part  of  the  acid- 
ity, but  the  CO  must  be  the  cause  of  some  of  the  acidity. 

This  is  shown  by  the  fact  that  the  samples  when  boiled  with 
water  for  several  hours  showed  no  greater,  and  in  most  cases, 
less  acidity  than  those  digested  with  warm  water  for  a short 
t ime . 

These  acid  values  will  be  of  use  in  calculating  the 
composition  of  a remover  for  carbon.  Knowing  the  acid  num- 
bers of  the  average  samples,  it  is  possible  to  determine  the 
proper  alkalinity  to  make  the  solvent.  The  relations  of  the 
elements  in  the  binding  compound  are  shown  to  be  (C5Hg0r,)n 
from  the  percentages  of  the  elements  found  in  the  extract  from 
the  Soxhlet  extraction.  It  is  this  type  of  hydrocarbon  that 
exerts  the  binding  influence  upon  the  metallic  particles  and 
the  soot.  Such  a compound  was  predicted  by  Mr.  T.  A.  Boyd 

g 

and  Mr.  C.  W.  Adams  of  the  General  Motors  Corporation. 

One  striking  feature  of  the  results  is  the  fact  that 
no  metals  of  the  alkaline  earth  family  were  present.  It  would 
be  supposed  that  when  silica  is  found  in  the  deposits,  some 
traces  of  calcium  or  like  metal  vtruld  be  present,  but  none 

w e it 

we*  found.  There  are  two  ways  of  explaining  this  absence; 
one  is  to  suppose  that  there  was  no  metal  with  the  silica; 
the  other,  that  the  silica  entered  as  some  silicate  of  iron. 

The  analysis  of  the  gases  given  off  at  105°C.  presents 
some  interesting  facts.  The  benzene  found  probably  results 
from  decomposition  of  the  fuels.  The  paraffins  can  not  be 
divided  into  percents  of  ethane  and  methane  as  is  usually  done 


. 


. 


. 


. 


' 

. 


. 


: 


; 

„ 

. 

. 


23 


in  flue  gas  analysis.  It  is  not  known  just  what  they  are, 

"but  it  is  to  be  expected  that  they  are  some  higher  homologues 

of  the  series  C H . such  as  hexane,  heptane,  or  octane, 
n 2n  4-  2, 

The  absence  of  unsaturated  compounds  and  carbon  monoxide 
is  contrary  to  what  might  be  expected.  The  oxygen  present  is 
due  to  the  adsorption  by  the  carbon.  The  moisture  content  is 
evidently  due  to  the  hydroscopic  character  of  the  deposits. 

It  could  not  be  present  in  the  original  sample  before  taking 
from  the  engine,  but  has  been  taken  up  by  the  material  while 
the  garage  man  was  finishing  the  removing  operation,  or  while 
the  bottle  was  uncorked  in  the  garage. 


« 


. •• 

. 

. 

« 


. 


24 


VI  .SUMMARY 

1.  Ultimate  and  proximate  analyses  were  given  for  the  deposit* 

2.  It  was  shown  that  there  was  less  road  dust  present  than 

was  commonly  supposed  to  he  there. 

3.  The  results  for  the  percentages  of  carbon,  hydrogen  and 
ash  were  shown  to  agree  with  those  obtained  by  other  work- 
ers using  samples  from  different  states. 

4.  The  sulphur  content  was  shown  to  be  higher  than  was  to 
be  expected,  and  its  significance  discussed. 

5.  The  compound  was  shown  to  be  distinctly  acid  and  the 
sources  of  this  acidity  were  given. 

6.  The  importance  of  knowing  the  acidity  was  given. 

7.  It  was  shown  that  no  relation  existed  between  the  character 
of  the  deposit  and  the  type  of  clyinder  oil  used. 

8.  The  absence  of  alkali  metals  and  alkaline- earth  metals 
was  proven. 

9.  The  presence  of  paraffin  hydrocarbons  and  moisture  was 
discussed. 

10.  The  matter  of  combustion  in  engine  cylinders  was  dis- 
cussed and  proof  was  given  that  the  carbon  deposits  were 
the  result  of  incomplete  combustion  rather  than  oil 
residues. 


. 

. 

V 


. 

. 

. 


. 


. 


, 

* 


. 

► 


. 


25. 


VII.  BIBLIOGRAPHY 

1.  Boyd,  T.  A.  J.  Ind.  Eng.  Chem.  13»  836  (1921) 

, 2.  White,  David  J.  Soc.  Automotive  Eng.  12,  561  (1919) 

3.  U.S.  Bureau  of  Standards,  Bulletin  99  "Carbonization  of 
Lubricating  Oils. " (Nov.  1920.) 

4.  Ikert,  B.  M.  Motor  Age  <34,  24-5  (July  18,  1921) 

5.  Ikert,  B.  M.  Unpublished  communication  (April  11,  1922) 

6.  Kettering,  C.  W.  Unpublished  communication  (Nov.  5,  1921) 

7.  Marcusson,  J.  J.  Soc.  ^ham.  Ind.  40.  289A  (1921) 

8.  Dickinson,  H.  C.  (National  Research  Council)  Unpublished 
communication  (Dec.  2,  1921) 

9.  Garner,  F.  H.  Gas  World  74  84-5  (1921) 

10.  Katz,  S.  H.  U.S.  Bureau  of  Mines.  Technical  Paper  183  (1918) 

11.  Sargent,  C.  E.  Private  Conversation  (Dec.  4,  1921) 

12.  Robinson,  F.  C.  Atlantic  Lubricator  3,  p.8  (Feb.  1920) 

13.  Boyd,  T.  A.  Unpublished  communication  (April  6,  1922) 

14.  Waters,  C.  E.  TJ.S.  Bureau  of  Standards.  Unpublished  com- 
munication. (Dec.  8,  1921) 


